An EFEM (Equipment Front End Module) is a device for passing a wafer between a processing apparatus configured to perform wafer processing and a wafer cassette having a plurality of wafer storage slots under clean conditions. A conveyor robot is provided inside the EFEM to convey the wafer between the wafer cassette and the wafer stage which are located upstream of the processing apparatus.
Such a conveyor robot is required to convey the wafer between the wafer cassette and the wafer stage without damaging the wafer. In recent years, various approaches have been made to increase the wafer conveyance speed. For example, a large number of conventional conveyor robots offer an increased conveyance speed by being provided with a plurality of arms (see Patent Document 1 for example).    Patent Document 1: Japanese Patent Laid-Open Publication No. 2002-158272